LAS VEGAS - US Senator John Ensign’s parents gave the Nevada Republican’s mistress and her family nearly $100,000 “out of concern for the well-being of longtime family friends during a difficult time,’’ a lawyer for the senator said yesterday.

In a statement sent to reporters, Paul Coggins described the payment as a single check for $96,000 given to Cindy and Doug Hampton and two of their children. It was given in April 2008, Coggins said, after the senator told his parents of his affair with Cindy Hampton, a campaign aide and longtime friend.

“None of the gifts came from campaign or official funds, nor were they related to any campaign or official duties,’’ the statement said. “Senator Ensign has complied with all applicable laws and Senate ethics rules.’’

The statement was made a day after Doug Hampton told a Las Vegas television show that Ensign, 51, paid Cindy Hampton more than $25,000 in severance when she left her job as treasurer for two Ensign-controlled campaign committees.

Ensign had not commented directly on allegations of payments to the Hamptons, but through a spokesman called Doug Hampton’s statements “consistently inaccurate.’’

A Washington watchdog group has said such a payment could have violated campaign finance laws because it was not reported by the committees.

Citizens for Responsibility and Ethics in Washington has sought a Senate ethics investigation and yesterday sent a letter to Attorney General Eric Holder asking for a criminal probe into the matter.

Coggins said no laws were violated with the $96,000 check.

“The gifts are consistent with a pattern of generosity by the Ensign family to the Hamptons and others,’’ he said.